1. Field of the Invention
This invention is concerned with the oligomerization of certain olefin mixtures to produce synthetic lubricant base stocks having improved viscosity characteristics.
2. Description of the Prior Art
In polymerization and oligomerization processes, recycle of light boiling fractions to the process has been used for increasing ultimate yield, hopefully without degrading the physical properties of the finished product. In the oligomerization of mixtures of short chain and long chain 1-olefins in the presence of Friedel-Crafts catalysts to produce super-quality synthetic lubricants, it was found that with catalysts, such as aluminum chloride, the use of recycle did indeed increase ultimate yield. The physical properties of the finished product, however, were either unfavorable or showed little change compared with properties obtained when recycle operation was not used. On the other hand, when water or alcohol promoted boron trifluoride catalyst was used, product yield remained essentially the same. Unexpectedly, however, fluid viscosity markedly decreased, accompanied by improvement in viscosity index. Both properties are considered highly important for a high quality synthetic lubricant.